agent/snmpd.c

/*
 * snmpd.c
 */
/** @defgroup agent The snmp agent
 * The snmp agent responds to SNMP queries from management stations
 */
/*
	Copyright 1988, 1989 by Carnegie Mellon University

                      All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the name of CMU not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.  

CMU DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
CMU BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.
******************************************************************/
#include <net-snmp/net-snmp-config.h>

#include <stdio.h>
#include <errno.h>
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <sys/types.h>
#if HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#if HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#if TIME_WITH_SYS_TIME
# ifdef WIN32
#  include <sys/timeb.h>
# else
#  include <sys/time.h>
# endif
# include <time.h>
#else
# if HAVE_SYS_TIME_H
#  include <sys/time.h>
# else
#  include <time.h>
# endif
#endif
#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#if HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#elif HAVE_WINSOCK_H
#include <winsock.h>
#endif
#if HAVE_NET_IF_H
#include <net/if.h>
#endif
#if HAVE_INET_MIB2_H
#include <inet/mib2.h>
#endif
#if HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif
#if HAVE_SYS_FILE_H
#include <sys/file.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#if HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif
#include <signal.h>
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#if HAVE_PROCESS_H  /* Win32-getpid */
#include <process.h>
#endif
#if HAVE_LIMITS_H
#include <limits.h>
#endif
#if HAVE_PWD_H
#include <pwd.h>
#endif
#if HAVE_GRP_H
#include <grp.h>
#endif

#ifndef PATH_MAX
# ifdef _POSIX_PATH_MAX
#  define PATH_MAX _POSIX_PATH_MAX
# else
#  define PATH_MAX 255
# endif
#endif

#ifndef FD_SET
typedef long    fd_mask;
#define NFDBITS (sizeof(fd_mask) * NBBY)        /* bits per mask */
#define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
#define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
#define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
#define FD_ZERO(p)      memset((p), 0, sizeof(*(p)))
#endif

#if HAVE_DMALLOC_H
#include <dmalloc.h>
#endif

#include "asn1.h"
#include "snmp_api.h"
#include "snmp_impl.h"
#include "system.h"
#include "read_config.h"
#include "snmp.h"
#include "mib.h"
#include "m2m.h"
#include "snmp_vars.h"
#include "agent_read_config.h"
#include "snmpv3.h"
#include "callback.h"
#include "snmp_alarm.h"
#include "default_store.h"
#include "mib_module_config.h"

#include "snmp_client.h"
#include "snmpd.h"
#include "agent_handler.h"
#include "var_struct.h"
#include "mibgroup/struct.h"
#include "snmp_debug.h"
#include "mib_modules.h"

#include "snmp_secmod.h"
#include "snmpusm.h"
#include "tools.h"
#include "lcd_time.h"
#include "mibgroup/util_funcs.h"

#include "snmp_agent.h"
#include "agent_trap.h"
#include "ds_agent.h"
#include "agent_read_config.h"
#include "snmp_logging.h"
#include "snmp_transport.h"

#include "version.h"

#include <net-snmp/agent/table.h>
#include <net-snmp/agent/table_iterator.h>
#include "mib_module_includes.h"

/*
 * Globals.
 */
#ifdef USE_LIBWRAP
#include <tcpd.h>

int allow_severity	 = LOG_INFO;
int deny_severity	 = LOG_WARNING;
#endif  /* USE_LIBWRAP */

#define TIMETICK         500000L
#define ONE_SEC         1000000L

int 		snmp_dump_packet;
int             running          = 1;
int		reconfig	 = 0;


extern char **argvrestartp;
extern char  *argvrestart;
extern char  *argvrestartname;

#define NUM_SOCKETS	32

#ifdef USING_SMUX_MODULE
static int sdlist[NUM_SOCKETS], sdlen = 0;
#endif /* USING_SMUX_MODULE */

/*
 * Prototypes.
 */
int snmp_read_packet (int);
int snmp_input (int, struct snmp_session *, int, struct snmp_pdu *, void *);
static void usage (char *);
int main (int, char **);
static void SnmpTrapNodeDown (void);
static int receive(void);

static void usage(char *prog)
{
        printf("\nUsage:  %s [OPTIONS] [ADDRESSES]", prog);
	printf("\n");
	printf("\n\tVersion:  %s\n",VersionInfo);
	printf("\tWeb:      http://www.net-snmp.org/\n");
	printf("\tEmail:    net-snmp-coders@lists.sourceforge.net\n");
	printf("\n  -a\t\t\tlog addresses\n");
 	printf("  -A\t\t\tappend to the logfile rather than truncating it\n");
	printf("  -c FILE\t\tread FILE as a configuration file\n");
	printf("  -C\t\t\tdo not read the default configuration files\n");
	printf("  -d\t\t\tdump sent and received SNMP packets\n");
	printf("  -D\t\t\tturn on debugging output\n");
	printf("  -f\t\t\tdo not fork from the shell\n");
#if HAVE_UNISTD_H
	printf("  -g GID\t\tchange to this numeric gid after opening\n\t\t\t  transport endpoints\n");
#endif
	printf("  -h, --help\t\tdisplay this usage message\n");
	printf("  -H\t\t\tdisplay configuration file directives understood\n");
	printf("  -I [-]INITLIST\tlist of mib modules to initialize (or not)\n");
	printf("\t\t\t  (run snmpd with -Dinit_mib for a list)\n");
	printf("  -l FILE\t\tprint warnings/messages to FILE\n");
#ifdef LOGFILE
	printf("\t\t\t  (by default FILE=%s)\n", LOGFILE);
#else
	printf("\t\t\t  (by default FILE=none)\n");
#endif
	printf("  -L\t\t\tprint warnings/messages to stdout/err\n");
	printf("  -P FILE\t\tstore process id in FILE\n");
	printf("  -q\t\t\tprint information in a more parsable format\n");
	printf("  -r\t\t\tdo not exit if files only accessible to root\n\t\t\t  cannot be opened\n");
	printf("  -s\t\t\tlog warnings/messages to syslog\n");
#if HAVE_UNISTD_H
	printf("  -u UID\t\tchange to this uid (numeric or textual) after\n\t\t\t  opening transport endpoints\n");
#endif
	printf("  -v, --version\t\tdisplay version information\n");
	printf("  -V\t\t\tverbose display\n");
#if defined(USING_AGENTX_SUBAGENT_MODULE)|| defined(USING_AGENTX_MASTER_MODULE)
	printf("  -x ADDRESS\t\tuse ADDRESS as AgentX address\n");
#endif
#ifdef USING_AGENTX_SUBAGENT_MODULE
	printf("  -X\t\t\trun as an AgentX subagent rather than as an\n\t\t\t  SNMP master agent\n");
#endif

	printf("\n");
	exit(1);
}

static void
version(void)
{
    printf("\nUCD-snmp version:  %s\n",VersionInfo);
    printf("Web:               http://www.net-snmp.org/\n");
    printf("Email:             net-snmp-coders@lists.sourceforge.net\n\n");
    exit(0);
}

	RETSIGTYPE
SnmpdShutDown(int a)
{
	running = 0;
}

#ifdef SIGHUP
	RETSIGTYPE
SnmpdReconfig(int a)
{
	reconfig = 1;
	signal(SIGHUP, SnmpdReconfig);
}
#endif

#ifdef SIGUSR1
extern void dump_registry( void );
	RETSIGTYPE
SnmpdDump(int a)
{
	dump_registry();
	signal(SIGUSR1, SnmpdDump);
}
#endif


	static void
SnmpTrapNodeDown(void)
{
    send_easy_trap (SNMP_TRAP_ENTERPRISESPECIFIC, 2);
    /* XXX  2 - Node Down #define it as NODE_DOWN_TRAP */
}

/*******************************************************************-o-******
 * main
 *
 * Parameters:
 *	 argc
 *	*argv[]
 *      
 * Returns:
 *	0	Always succeeds.  (?)
 *
 *
 * Setup and start the agent daemon.
 *
 * Also successfully EXITs with zero for some options.
 */
int
main(int argc, char *argv[])
{
    char options[128] = "aAc:CdD::fhHI:l:LP:qrsV";
    int  arg, i, ret;
    int  dont_fork = 0;
    int  dont_zero_log = 0;
    int  stderr_log=0, syslog_log=0;
    int  uid=0, gid=0;
    int  agent_mode=-1;
    char logfile[PATH_MAX + 1] = { 0 };
    char *cptr, **argvptr;
    char *pid_file = NULL;
#if HAVE_GETPID
    FILE *PID;
#endif

#ifdef LOGFILE
    strncpy(logfile, LOGFILE, PATH_MAX);
#endif

#ifdef NO_ROOT_ACCESS
    /*  Default to no.  */
    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_NO_ROOT_ACCESS, 1);
#endif
    /*  Default to NOT running an AgentX master.  */
    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_AGENTX_MASTER, 0);

    /*  Add some options if they are available.  */
#if HAVE_UNISTD_H
    strcat(options, "g:u:");
#endif
#if defined(USING_AGENTX_SUBAGENT_MODULE)|| defined(USING_AGENTX_MASTER_MODULE)
    strcat(options, "x:");
#endif
#ifdef USING_AGENTX_SUBAGENT_MODULE
    strcat(options, "X");
#endif

    /*  Initial scan for "--help" and "--version".  */
    
    for (i = 0; i < argc; i++) {
	if (strcmp(argv[i], "--help") == 0) {
	    usage(argv[0]);
	} else if (strcmp(argv[i], "--version") == 0) {
	    version();
	}
    }

    /*  Now process options normally.  */
    
    while ((arg = getopt(argc, argv, options)) != EOF) {
	switch (arg) {
	case 'a':
	    log_addresses++;
	    break;

	case 'A':
	    dont_zero_log = 1;
	    break;

	case 'c':
	    if (optarg != NULL) {
		ds_set_string(DS_LIBRARY_ID, DS_LIB_OPTIONALCONFIG, optarg);
	    } else {
		usage(argv[0]);
	    }		
	    break;

	case 'C':
	    ds_set_boolean(DS_LIBRARY_ID, DS_LIB_DONT_READ_CONFIGS, 1);
	    break;

	case 'd':
	    snmp_set_dump_packet(++snmp_dump_packet);
	    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_VERBOSE, 1);
	    break;

	case 'D':
	    debug_register_tokens(optarg);
	    snmp_set_do_debugging(1);
	    break;

	case 'f':
	    dont_fork = 1;
	    break;

#if HAVE_UNISTD_H
	case 'g':
	    if (optarg != NULL) {
		ds_set_int(DS_APPLICATION_ID, DS_AGENT_GROUPID,
			   atoi(optarg));
	    } else {
		usage(argv[0]);
	    }
	    break;
#endif
		
	case 'h':
	    usage(argv[0]);
	    break;

	case 'H':
	    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_NO_ROOT_ACCESS, 1);
	    init_agent("snmpd");   /* register our .conf handlers */
	    init_mib_modules();
	    init_snmp("snmpd");
	    fprintf(stderr, "Configuration directives understood:\n");
	    read_config_print_usage("  ");
	    exit(0);

	case 'I':
	    if (optarg != NULL) {
		add_to_init_list(optarg);
	    } else {
		usage(argv[0]);
	    }
	    break;

	case 'l':
	    if (optarg != NULL) {
		if (strlen(optarg) > PATH_MAX) {
		    fprintf(stderr,
			    "%s: logfile path too long (limit %d chars)\n",
			    argv[0], PATH_MAX);
		    exit(1);
		}
		strncpy(logfile, optarg, PATH_MAX);
	    } else {
		usage(argv[0]);
	    }
	    break;
		
	case 'L':
	    stderr_log=1;
	    break;

	case 'P':
	    if (optarg != NULL) {
		pid_file = optarg;
	    } else {
		usage(argv[0]);
	    }		
	    break;

	case 'q':
	    snmp_set_quick_print(1);
	    break;

	case 'r':
	    ds_toggle_boolean(DS_APPLICATION_ID, DS_AGENT_NO_ROOT_ACCESS);
	    break;

	case 's':
	    syslog_log=1;
	    break;

#if HAVE_UNISTD_H
	case 'u':
	    if (optarg != NULL) {
		char *ecp;
		int uid;

		uid = strtoul(optarg, &ecp, 10);
		if (*ecp) {
#if HAVE_GETPWNAM && HAVE_PWD_H
		    struct passwd *info;
		    info = getpwnam(argv[arg]);
		    if (info) {
			uid = info->pw_uid;
		    } else {
#endif
			fprintf(stderr, "Bad user id: %s\n", optarg);
			exit(1);
#if HAVE_GETPWNAM && HAVE_PWD_H
		    }
#endif
		}
		ds_set_int(DS_APPLICATION_ID, DS_AGENT_USERID, uid);
	    } else {
		usage(argv[0]);
	    }
	    break;
#endif

	case 'v':
	    version();

	case 'V':
	    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_VERBOSE, 1);
	    break;

#if defined(USING_AGENTX_SUBAGENT_MODULE)|| defined(USING_AGENTX_MASTER_MODULE)
	case 'x':
	    if (optarg != NULL) {
		ds_set_string(DS_APPLICATION_ID, DS_AGENT_X_SOCKET, optarg);
	    } else {
		usage(argv[0]);
	    }
	    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_AGENTX_MASTER, 1 );
	    break;
#endif

	case 'X':
#if defined(USING_AGENTX_SUBAGENT_MODULE)
	    agent_mode = SUB_AGENT;
#else
	    fprintf(stderr, "%s: Illegal argument -X: AgentX support not compiled in.\n", argv[0]);
	    usage(argv[0]);
	    exit(1);
#endif
	    break;

	default:
	    fprintf(stderr, "%s: Invalid option: -%c\n", argv[0], arg);
	    usage(argv[0]);
	    break;
	}
    }

    if (optind < argc) {
	/*  There are optional transport addresses on the command line.  */
	DEBUGMSGTL(("snmpd/main", "optind %d, argc %d\n", optind, argc));
	for (i = optind; i < argc; i++) {
	    char *c, *astring;
	    if ((c = ds_get_string(DS_APPLICATION_ID, DS_AGENT_PORTS))) {
		astring = malloc(strlen(c) + 2 + strlen(argv[i]));
		if (astring == NULL) {
		    fprintf(stderr, "malloc failure processing argv[%d]\n",
			    i);
		    exit(1);
		}
		sprintf(astring, "%s,%s", c, argv[i]);
		ds_set_string(DS_APPLICATION_ID, DS_AGENT_PORTS, astring);
		free(astring);
	    } else {
		ds_set_string(DS_APPLICATION_ID, DS_AGENT_PORTS, argv[i]);
	    }
	}
	DEBUGMSGTL(("snmpd/main", "port spec: %s\n",
		    ds_get_string(DS_APPLICATION_ID, DS_AGENT_PORTS)));
    }

    /*  Honor selection of standard error output.  */
    if (!stderr_log) {
	snmp_disable_stderrlog();
    }
    
    /*  Initialize a argv set to the current for restarting the agent.	*/
    argvrestartp = (char **)malloc((argc + 2) * sizeof(char *));
    argvptr = argvrestartp;
    for (i = 0, ret = 1; i < argc; i++) {
	ret += strlen(argv[i]) + 1;
    }
    argvrestart = (char *) malloc(ret);
    argvrestartname = (char *) malloc(strlen(argv[0]) + 1);
    strcpy(argvrestartname, argv[0]);
    if (agent_mode == -1) {
	if (strstr(argvrestartname, "agentxd") != NULL) {
	    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_ROLE, SUB_AGENT);
	} else {
	    ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_ROLE, MASTER_AGENT);
	}
    } else {
	ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_ROLE, agent_mode);
    }
        
    for (cptr = argvrestart, i = 0; i < argc; i++) {
	strcpy(cptr, argv[i]);
	*(argvptr++) = cptr;
	cptr += strlen(argv[i]) + 1;
    }
    *cptr = 0;
    *argvptr = NULL;

    /*  Open the logfile if necessary.  */

    /*  Should open logfile and/or syslog based on arguments.  */
    if (logfile[0]) {
	snmp_enable_filelog(logfile, dont_zero_log);
    }

    if (syslog_log) {
	snmp_enable_syslog(); 
    }

#ifdef BUFSIZ
    setvbuf(stdout, NULL, _IOLBF, BUFSIZ);
#endif
    /*  Initialize the world.  Detach from the shell.  Create initial user.  */
#if HAVE_FORK
    if (!dont_fork && fork() != 0) {
      exit(0);
    }
#endif

#if HAVE_GETPID
    if (pid_file != NULL) {
	if ((PID = fopen(pid_file, "w")) == NULL) {
	    snmp_log_perror("fopen");
	    if (!ds_get_boolean(DS_APPLICATION_ID, DS_AGENT_NO_ROOT_ACCESS)) {
		exit(1);
	    }
	} else {
	    fprintf(PID, "%d\n", (int)getpid());
	    fclose(PID);
	}
    }
#endif

    SOCK_STARTUP;
    init_agent("snmpd");		/* do what we need to do first. */
    init_mib_modules();
    
    /* start library */
    init_snmp("snmpd");

    if ((ret = init_master_agent()) != 0) {
	/*  Some error opening one of the specified agent transports.  */
	Exit(1); /*  Exit logs exit val for us  */
    }

#ifdef SIGTERM
    signal(SIGTERM, SnmpdShutDown);
#endif
#ifdef SIGINT
    signal(SIGINT, SnmpdShutDown);
#endif
#ifdef SIGHUP
    signal(SIGHUP, SnmpdReconfig);
#endif
#ifdef SIGUSR1
    signal(SIGUSR1, SnmpdDump);
#endif
#ifdef SIGPIPE
    signal(SIGPIPE, SIG_IGN);	/* 'Inline' failure of wayward readers */
#endif

    /*  Store persistent data immediately in case we crash later.  */
    snmp_store("snmpd");

    /*  Send coldstart trap if possible.  */
    send_easy_trap (0, 0);
        
#if HAVE_UNISTD_H
#ifdef HAVE_SETGID
    if ((gid = ds_get_int(DS_APPLICATION_ID, DS_AGENT_GROUPID)) != 0) {
	DEBUGMSGTL(("snmpd/main", "Changing gid to %d.\n", gid));
	if (setgid(gid)==-1
#ifdef HAVE_SETGROUPS
	    || setgroups(1, &gid)==-1
#endif
	    ) {
	    snmp_log_perror("setgid failed");
	    if (!ds_get_boolean(DS_APPLICATION_ID, DS_AGENT_NO_ROOT_ACCESS)) {
		exit(1);
	    }
	}
    }
#endif
#ifdef HAVE_SETUID
    if ((uid = ds_get_int(DS_APPLICATION_ID, DS_AGENT_USERID)) != 0) {
	DEBUGMSGTL(("snmpd/main", "Changing uid to %d.\n", uid));
	if(setuid(uid)==-1) {
	    snmp_log_perror("setuid failed");
	    if (!ds_get_boolean(DS_APPLICATION_ID, DS_AGENT_NO_ROOT_ACCESS)) {
		exit(1);
	    }
	}
    }
#endif
#endif

    /*  We're up, log our version number.  */
    snmp_log(LOG_INFO, "UCD-SNMP version %s\n", VersionInfo);
    snmp_addrcache_initialise();

    /*  Forever monitor the dest_port for incoming PDUs.  */
    DEBUGMSGTL(("snmpd/main", "We're up.  Starting to process data.\n"));
    receive();
#include "mib_module_shutdown.h"
    DEBUGMSGTL(("snmpd/main", "sending shutdown trap\n"));
    SnmpTrapNodeDown();
    DEBUGMSGTL(("snmpd/main", "Bye...\n"));
    snmp_shutdown("snmpd");
    return 0;
}  /* End main() -- snmpd */

/*******************************************************************-o-******
 * receive
 *
 * Parameters:
 *      
 * Returns:
 *	0	On success.
 *	-1	System error.
 *
 * Infinite while-loop which monitors incoming messges for the agent.
 * Invoke the established message handlers for incoming messages on a per
 * port basis.  Handle timeouts.
 */
static int
receive(void)
{
    int numfds;
    fd_set readfds, writefds, exceptfds;
    struct timeval	timeout, *tvp = &timeout;
    struct timeval	sched,   *svp = &sched,
			now,     *nvp = &now;
    int count, block, i;
#ifdef	USING_SMUX_MODULE
    int sd;
#endif	/* USING_SMUX_MODULE */


    /*
     * Set the 'sched'uled timeout to the current time + one TIMETICK.
     */
    gettimeofday(nvp, (struct timezone *) NULL);
    svp->tv_usec = nvp->tv_usec + TIMETICK;
    svp->tv_sec = nvp->tv_sec;
    
    while (svp->tv_usec >= ONE_SEC){
	svp->tv_usec -= ONE_SEC;
	svp->tv_sec++;
    }

    /*
     * Loop-forever: execute message handlers for sockets with data,
     * reset the 'sched'uler.
     */
    while (running) {
        if (reconfig) {
	    reconfig = 0;
	    snmp_log(LOG_INFO, "Reconfiguring daemon\n");
	    update_config();
        }

	for (i = 0; i < NUM_EXTERNAL_SIGS; i++) {
	    if (external_signal_scheduled[i]) {
		external_signal_scheduled[i]--;
		external_signal_handler[i](i);
	    }
	}

	tvp =  &timeout;
	tvp->tv_sec = 0;
	tvp->tv_usec = TIMETICK;

	numfds = 0;
	FD_ZERO(&readfds);
	FD_ZERO(&writefds);
	FD_ZERO(&exceptfds);
        block = 0;
        snmp_select_info(&numfds, &readfds, tvp, &block);
        if (block == 1)
            tvp = NULL; /* block without timeout */

#ifdef	USING_SMUX_MODULE
	if (smux_listen_sd >= 0) {
	    FD_SET(smux_listen_sd, &readfds);
	    numfds = smux_listen_sd >= numfds ? smux_listen_sd + 1 : numfds;
	    for (i = 0; i < sdlen; i++) {
		FD_SET(sdlist[i], &readfds);
		numfds = sdlist[i] >= numfds ? sdlist[i] + 1 : numfds;
	    }
	}
#endif	/* USING_SMUX_MODULE */

	for (i = 0; i < external_readfdlen; i++) {
	    FD_SET(external_readfd[i], &readfds);
	    if (external_readfd[i] >= numfds)
		numfds = external_readfd[i] + 1;
	}
	for (i = 0; i < external_writefdlen; i++) {
	    FD_SET(external_writefd[i], &writefds);
	    if (external_writefd[i] >= numfds)
		numfds = external_writefd[i] + 1;
	}
	for (i = 0; i < external_exceptfdlen; i++) {
	    FD_SET(external_exceptfd[i], &exceptfds);
	    if (external_exceptfd[i] >= numfds)
		numfds = external_exceptfd[i] + 1;
	}

	count = select(numfds, &readfds, &writefds, &exceptfds, tvp);
	DEBUGMSGTL(("snmpd/select", "returned, count = %d\n", count));

	if (count > 0) {

#ifdef USING_SMUX_MODULE 
            /* handle the SMUX sd's */ 
            if (smux_listen_sd >= 0) { 
                for (i = 0; i < sdlen; i++) { 
                    if (FD_ISSET(sdlist[i], &readfds)) { 
                        if (smux_process(sdlist[i]) < 0) { 
                            for (; i < (sdlen - 1); i++) { 
                                sdlist[i] = sdlist[i+1]; 
                            } 
                            sdlen--; 
                        } 
                    } 
                } 
                /* new connection */ 
                if (FD_ISSET(smux_listen_sd, &readfds)) { 
                    if ((sd = smux_accept(smux_listen_sd)) >= 0) { 
                        sdlist[sdlen++] = sd; 
                    } 
                } 
            } 
#endif /* USING_SMUX_MODULE */ 

	    snmp_read(&readfds);

	    for (i = 0; count && (i < external_readfdlen); i++) {
		if (FD_ISSET(external_readfd[i], &readfds)) {
		    external_readfdfunc[i](external_readfd[i],
					   external_readfd_data[i]);
		    FD_CLR(external_readfd[i], &readfds);
		    count--;
		}
	    }
	    for (i = 0; count && (i < external_writefdlen); i++) {
		if (FD_ISSET(external_writefd[i], &writefds)) {
		    external_writefdfunc[i](external_writefd[i],
					    external_writefd_data[i]);
		    FD_CLR(external_writefd[i], &writefds);
		    count--;
		}
	    }
	    for (i = 0; count && (i < external_exceptfdlen); i++) {
		if (FD_ISSET(external_exceptfd[i], &exceptfds)) {
		    external_exceptfdfunc[i](external_exceptfd[i],
					     external_exceptfd_data[i]);
		    FD_CLR(external_exceptfd[i], &exceptfds);
		    count--;
		}
	    }
	    
	} else switch (count) {
	    case 0:
                snmp_timeout();
                break;
	    case -1:
		if (errno == EINTR) {
		    continue;
		} else {
                    snmp_log_perror("select");
		}
		return -1;
	    default:
		snmp_log(LOG_ERR, "select returned %d\n", count);
		return -1;
	}  /* endif -- count>0 */




        /*
         * If the time 'now' is greater than the 'sched'uled time, then:
         *
         *    Check alarm and event timers.
         *    Reset the 'sched'uled time to current time + one TIMETICK.
         *    Age the cache network addresses (from whom messges have
         *        been received).
         */
        gettimeofday(nvp, (struct timezone *) NULL);

        if (nvp->tv_sec > svp->tv_sec
                || (nvp->tv_sec == svp->tv_sec && nvp->tv_usec > svp->tv_usec)){
            svp->tv_usec = nvp->tv_usec + TIMETICK;
            svp->tv_sec = nvp->tv_sec;

            while (svp->tv_usec >= ONE_SEC){
                svp->tv_usec -= ONE_SEC;
                svp->tv_sec++;
            }
            if (log_addresses && lastAddrAge++ > 600) {
	      snmp_addrcache_age();
            }
        }  /* endif -- now>sched */

        /* run requested alarms */
        run_alarms();
        
        check_outstanding_agent_requests(SNMP_ERR_NOERROR);

    }  /* endwhile */

    snmp_log(LOG_INFO, "Received TERM or STOP signal...  shutting down...\n");
    return 0;

}  /* end receive() */



/*******************************************************************-o-******
 * snmp_input
 *
 * Parameters:
 *	 op
 *	*session
 *	 requid
 *	*pdu
 *	*magic
 *      
 * Returns:
 *	1		On success	-OR-
 *	Passes through	Return from alarmGetResponse() when 
 *	  		  USING_V2PARTY_ALARM_MODULE is defined.
 *
 * Call-back function to manage responses to traps (informs) and alarms.
 * Not used by the agent to process other Response PDUs.
 */
int
snmp_input(int op,
	   struct snmp_session *session,
	   int reqid,
	   struct snmp_pdu *pdu,
	   void *magic)
{
    struct get_req_state *state = (struct get_req_state *)magic;
    
    if (op == SNMP_CALLBACK_OP_RECEIVED_MESSAGE) {
	if (pdu->command == SNMP_MSG_GET) {
	    if (state->type == EVENT_GET_REQ) {
		/* this is just the ack to our inform pdu */
		return 1;
	    }
	}
    }
    else if (op == SNMP_CALLBACK_OP_TIMED_OUT) {
	if (state->type == ALARM_GET_REQ) {
		/* Need a mechanism to replace obsolete SNMPv2p alarm */
	}
    }
    return 1;

} /* end snmp_input() */